Date: 14-02-06 13:46
A lot of ISPs (including me) use port 2525 to allow users to relay email.
In postfix, all I had to do was add;
2525 inet n - n - - smtpd
right after the smtp line in the master.cf.
I have also setup several Sendmail servers to listen on port 2525 as well. Yuo cna lock down these to require SMTP AUTH on those ports to do anything. In the sendmail.mc file I changed so many things it is hard to remomber where I started. But this is right from a working sendmail box;
DAEMON_OPTIONS(`Port=25, Name=MTA, M=E')
DAEMON_OPTIONS(`Port=2525, Name=MTA, M=Ea')
The "E" is for ESTMP, and the "a" is for the SMTP AUTH.